TULSA — The Oklahoma state medical examiner's office is investigating after a human skull was discovered on the grounds of a Tulsa casino.

Tulsa Police Sgt. Dave Walker said Lighthorse police found the skull Saturday night at the River Spirit Casino grounds. Walker said authorities later discovered bones from a human foot in a nearby drainage ditch.

Lighthorse police were assisted by the Federal Bureau of Investigation with the search.

Walker told the Tulsa World that the skull was mummified and that an expert believes it may have been on casino property for about a year. Walker says there's no sign of trauma to the skull and investigators are working to identify the remains using DNA.